U.S. patent number 10,394,218 [Application Number 15/512,725] was granted by the patent office on 2019-08-27 for vibration cutting process diagnostic device.
This patent grant is currently assigned to Mitsubishi Electric Corporation. The grantee listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Toshihiro Azuma, Kotaro Nagaoka, Akira Tanabe.
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United States Patent |
10,394,218 |
Nagaoka , et al. |
August 27, 2019 |
Vibration cutting process diagnostic device
Abstract
A vibration cutting process diagnostic device diagnoses the
propriety of a vibration cutting process to machine the sectional
shape of a working object into a non-complete round shape by
reciprocating a movable shaft. This device includes a frequency
analyzer to calculate a frequency component contained in a position
command signal for the movable shaft on the basis of shape data,
which is machining shape data on a workpiece treated as the working
object, and a machining speed set value; and a process diagnosis
executor to diagnose the propriety of machining the shape data
under the machining speed set value on the basis of the frequency
component and a movable shaft parameter of the movable shaft.
Inventors: |
Nagaoka; Kotaro (Tokyo,
JP), Tanabe; Akira (Tokyo, JP), Azuma;
Toshihiro (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Chiyoda-ku, Tokyo |
N/A |
JP |
|
|
Assignee: |
Mitsubishi Electric Corporation
(Tokyo, JP)
|
Family
ID: |
55746297 |
Appl.
No.: |
15/512,725 |
Filed: |
October 17, 2014 |
PCT
Filed: |
October 17, 2014 |
PCT No.: |
PCT/JP2014/077748 |
371(c)(1),(2),(4) Date: |
March 20, 2017 |
PCT
Pub. No.: |
WO2016/059729 |
PCT
Pub. Date: |
April 21, 2016 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170300034 A1 |
Oct 19, 2017 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G05B
19/406 (20130101); B23Q 15/013 (20130101); G05B
19/4065 (20130101); B23Q 15/08 (20130101); B23B
5/36 (20130101); G05B 2219/37087 (20130101); G05B
2219/39241 (20130101) |
Current International
Class: |
G05B
19/4065 (20060101); G05B 19/406 (20060101); B23Q
15/013 (20060101); B23Q 15/08 (20060101); B23B
5/36 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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102870055 |
|
Jan 2013 |
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CN |
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1-271102 |
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Oct 1989 |
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JP |
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2-036045 |
|
Feb 1990 |
|
JP |
|
2-205439 |
|
Aug 1990 |
|
JP |
|
3-178703 |
|
Aug 1991 |
|
JP |
|
6-083417 |
|
Mar 1994 |
|
JP |
|
2007-033244 |
|
Feb 2007 |
|
JP |
|
2008-068364 |
|
Mar 2008 |
|
JP |
|
2008-087146 |
|
Apr 2008 |
|
JP |
|
2009-055677 |
|
Mar 2009 |
|
JP |
|
2012-053509 |
|
Mar 2012 |
|
JP |
|
Other References
Japanese Office Action for JP 2015-537475 dated Nov. 17, 2015.
cited by applicant .
Taiwanese Office Action TW 10520705520 dated Jun. 6, 2016. cited by
applicant .
International Search Report of PCT/JP2014/077748, dated Jan. 20,
2015. cited by applicant .
Communication dated Nov. 2, 2018 from the State Intellectual
Property Office of the P.R.C. in counterpart Chinese application
No. 201480082701.2. cited by applicant.
|
Primary Examiner: Ortiz Rodriguez; Carlos R
Attorney, Agent or Firm: Sughrue Mion, PLLC Turner; Richard
C.
Claims
The invention claimed is:
1. A vibration cutting process diagnostic device that is capable of
diagnosing, before machining, propriety of a vibration cutting
process used when a movable shaft is reciprocated to machine a
sectional shape of a working object into a non-complete round
shape, the device comprising: a frequency analyzer to calculate a
frequency component contained in a position command signal for the
movable shaft on a basis of machining shape data on the working
object and a machining speed set value; and a process diagnosis
executor to diagnose propriety of machining the machining shape
data under the machining speed set value on a basis of the
frequency component, and a movable shaft parameter of the movable
shaft, wherein the process diagnosis executor calculates a range of
machining speeds that makes the process performable or a range of
machining speeds that makes the process unperformable, and causes
the display the range.
2. The vibration cutting process diagnostic device according to
claim 1, wherein the movable shaft is driven by a control system
having a characteristic of a low-pass filter; the movable shaft
parameter includes a cutoff frequency of the low-pass filter; and
if the frequency component is not less than the cutoff frequency,
the process is diagnosed to be unperformable.
3. The vibration cutting process diagnostic device according to
claim 1, wherein the movable shaft is driven by a control system
having a characteristic of a band elimination filter; the movable
shaft parameter includes a cutoff frequency band of the band
elimination filter; and if the frequency component falls within the
cutoff frequency band, the process is diagnosed to be
unperformable.
4. The vibration cutting process diagnostic device according to
claim 1, wherein the movable shaft forms part of a mechanical
system having an anti-resonance characteristic; the movable shaft
parameter includes the anti-resonance frequency of the mechanical
system of the movable shaft; and if the frequency component is
equal to the anti-resonance frequency, the process is diagnosed to
be unperformable.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a National Stage of International Application
No. PCT/JP2014/077748 filed Oct. 17, 2014, the contents of all of
which are incorporated herein by reference in their entirety.
FIELD
The present invention relates to a vibration cutting process
diagnostic device that is used when a reciprocating tool is used
during a vibration cutting process to machine the sectional shape
of a working object into a non-complete round shape; and that can
diagnose the propriety of the process in advance of it being
performed.
BACKGROUND
In relation to machine tools for performing a cutting process,
there has been proposed various machining apparatuses and machining
methods to perform a process that could not be done conventionally.
One of the examples is a vibration cutting process in which a tool
is reciprocated for a rotation-cutting process at a high speed to
form a non-complete round shape.
According to a conventional rotation-cutting process, there is used
a machine that includes a main shaft for rotating a workpiece and a
rectilinear shaft for moving a tool bit, which is an example of a
tool, in the radial direction of the workpiece. The tool is moved
to a commanded position on the rectilinear shaft and is brought
into contact with the workpiece being rotated, and thereby the
sectional shape of the working object is machined into a complete
round shape. At this time, if, while the workpiece is rotated, the
tool is moved in the radial direction by reciprocating the tool on
the rectilinear shaft, the workpiece can be machined into a
non-complete round shape. For example, if the tool is reciprocated
twice on the rectilinear shaft toward the center of the workpiece
while the workpiece is rotated once, the sectional shape of the
working object can be made into an elliptical shape. Specifically,
the elliptical shape is formed such that its minor axis is defined
by a distance between the tip of the tool and the center of the
rotary shaft obtained at the time when the tool is positioned
closest to the center of the workpiece, and such that its major
axis is defined by a distance between the tip of the tool and the
center of the rotary shaft obtained at the time when the tool is
positioned farthest from the center of the workpiece. Further, the
workpiece can be machined into a more complicated shape by
deliberately adjusting the reciprocating motion pattern.
Further, Patent Literature 1 discloses a vibration cutting
apparatus and a vibration cutting method that can machine a working
object into a non-complete round shape. According to a technique
disclosed in Patent Literature 1, a machine having rectilinear
shafts of two axes or more is used to machine a working object into
a non-complete round shape by giving periodic motion commands with
different phase and amplitude to two shafts of the rectilinear
shafts.
As described above, when a working object is machined into a
non-complete round shape, a rectilinear shaft makes a sine
wave-like motion which may contain a harmonic component depending
on the curvature of the commanded machining shape. On the other
hand, a motor control unit for a machine tool requires position
control with higher speed and higher accuracy. However, if the
feeding speed is set higher to increase the throughput rate or if
the control gain is set higher to improve the accuracy, machine
natural vibration is excited and machine resonance is thereby
caused. Consequently the behavior becomes vibratory and the
machining accuracy is lowered.
Conventionally, in consideration of the above, a filter for
treating a position command signal is used to remove the machine
natural vibration. The filter used is generally called "band
elimination filter" or "low-pass filter" and is set to remove a
specific frequency band component with respect to the position
command signal or another state quantity inside the control unit,
thereby preventing excitation of the machine natural vibration.
If the machine resonance is caused by a specific frequency, a band
elimination filter for attenuating a frequency band component
including this frequency is operated onto the position command
signal. Here, if the frequency band is narrow, a notch filter can
be used in place of the band elimination filter. Further, if the
machine resonance is caused by a frequency of not less than a
specific value and the frequency varies depending on the mass or
another condition of a workpiece, a low-pass filter for attenuating
the frequency component higher than the frequency is operated onto
the position command signal. When a filter for treating the
position command signal in this way is used, it becomes possible to
realize a process with higher speed and higher accuracy without
excitations of the machine resonances. In general, a frequency
component contained in the position command signal is far lower
than the cutoff frequency of a band elimination filter, notch
filter, or low-pass filter that are operated thereon, so that the
process for a commanded shape can be performed even if the filter
is operated thereon.
CITATION LIST
Patent Literature
Patent Literature 1: Japanese Patent Application Laid-open No.
2008-68364
SUMMARY
Technical Problem
However, according to the conventional technique of Patent
Literature 1 described above, in the case of an application for
performing a process by reciprocating a tool at a high speed, there
is a phenomenon as follows: A position command signal for the
rectilinear shaft for moving the tool in the radial direction
includes a frequency component determined by the period of the tool
reciprocating motion. As the machining shape to be commanded
becomes more complicated, the position command signal comes to
contain a higher harmonic wave. As the feeding speed is higher, the
frequency component contained in the position command signal
becomes higher. Consequently, if the frequency component contained
in the position command signal is equal to the cutoff frequency
band of a filter in the control unit, or if the frequency component
falls within the cutoff frequency band, the machining accuracy is
lowered and the working object cannot be machined into a desired
shape, which is a problem.
Further, if anti-resonance is present in a mechanical system, the
reaction of the mechanical system becomes slow with respect to a
position command signal component near to the anti-resonance
frequency. Consequently, a problem arises such that the machining
accuracy is lowered.
Further, as a result of actually performing a trial process, if the
machining accuracy is low, it is difficult to sort out the causes,
and it becomes necessary to perform a search by try and error for
the feeding speed and the main shaft revolution number, which are
examples of the command conditions suitable for obtaining a desired
machining accuracy. Consequently, a problem arises such that a
large number of steps are required to determine the command
conditions.
The present invention has been made in view of the above, and an
objective of the present invention is to provide a vibration
cutting process diagnostic device that can be used for a vibration
cutting process to machine the sectional shape of a working object
into a non-complete round shape by reciprocating a tool for a
rotation-cutting process and that can diagnose the propriety of the
vibration cutting process under a speed condition specified for
vibration cutting in advance of the process being performed.
Solution to Problem
In order to solve the problem and achieve the objective the present
invention relates to a vibration cutting process diagnostic device
for diagnosing propriety of a vibration cutting process used when a
movable shaft is reciprocated to machine a sectional shape of a
working object into a non-complete round shape. The vibration
cutting process diagnostic device includes: a frequency analyzer to
calculate a frequency component contained in a position command
signal for the movable shaft on a basis of machining shape data on
the working object and a machining speed set value; and a process
diagnosis executor to diagnose propriety of machining the machining
shape data under the machining speed set value on a basis of the
frequency component and a movable shaft parameter of the movable
shaft.
Advantageous Effects of Invention
The vibration cutting process diagnostic device according to the
present invention provides an effect capable of realizing a
vibration cutting process diagnosis for machining the sectional
shape of a working object into a non-complete round shape by
reciprocating a tool for a rotation-cutting process and capable of
diagnosing the propriety of the vibration cutting process under a
speed condition specified for vibration cutting, in advance of the
process being performed.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a block diagram illustrating a configuration of a
vibration cutting process diagnostic device according to a first
embodiment.
FIG. 2 is a schematic view illustrating a configuration example of
the mechanical system of a lathe in the first embodiment.
FIG. 3 is a graph illustrating a frequency analysis result obtained
by a frequency analysis unit in the first embodiment.
FIG. 4 is a graph illustrating a frequency analysis result obtained
by the frequency analysis unit in a second embodiment.
FIG. 5 is a view illustrating an example of the gain response
characteristics of a mechanical system in the second
embodiment.
DESCRIPTION OF EMBODIMENTS
Exemplary embodiments of a vibration cutting process diagnostic
device according to the present invention will be explained below
in detail with reference to the accompanying drawings. The present
invention is not limited to the following embodiments.
First Embodiment
FIG. 1 is a block diagram illustrating a configuration of a
vibration cutting process diagnostic device according to a first
embodiment of the present invention. The vibration cutting process
diagnostic device 10 illustrated in FIG. 1 is a device for
diagnosing the propriety of a vibration cutting process used when a
rectilinear shaft of a tool rest 14, which serves as a movable
shaft, is reciprocated in order to machine the sectional shape of a
working object into a non-complete round shape. This device
includes a frequency analysis unit 4 to read working object shape
data 1 and a machining speed set value 2 and then to calculate on
the basis thereon a frequency component contained in a position
command signal for the movable shaft; and a process diagnosis
execution unit 5 to diagnose the propriety of machining the shape
data 1 under the machining speed set value 2 on the basis of the
frequency component calculated by the frequency analysis unit 4 and
a movable shaft parameter 3 of the movable shaft. Here, the movable
shaft collectively means a mechanism for moving the tool rest 14;
and the rectilinear shaft means a drive shaft of the tool rest 14,
which is one form of the movable shaft and serves as a drive
mechanism for moving the tool rest 14 in a straight line.
FIG. 2 is a schematic view illustrating a configuration example of
the mechanical system of a lathe. A workpiece 12 is attached to a
rotation-cutting main shaft 11 to be rotated; and a
rotation-cutting tool 15 is attached to the tool rest 14. The tool
rest 14 is reciprocated in the radial direction by a tool rest
drive unit 13. If the tool rest 14 is reciprocated twice while the
rotation-cutting main shaft 11 is rotated once, the workpiece 12
can be machined into the shape of an elliptical column. Further, if
the tool rest 14 is reciprocated a greater number of times, the
sectional shape of the workpiece 12 can be machined into a more
complicated shape.
When the shape data 1, which is data on the sectional shape after
the process on the workpiece 12 to be machined, and the machining
speed set value 2, which is the rotational speed of the
rotation-cutting main shaft 11, are set, then the frequency
analysis unit 4 performs polar coordinate transformation on the
shape data 1, and thereby obtains a deflection angle and a radial
direction displacement. Here, the radial direction is a radial
direction with respect to the rotational axis of the
rotation-cutting main shaft 11. In this example, the radial
direction is defined by a line segment extending from the contact
surface of the rotation-cutting tool 15 toward the center of the
sectional shape of the workpiece 12. Time-series variations in the
radial direction displacement are then obtained, in a case where an
interpolation is performed by changing the deflection angle from
0.degree. to 360.degree. at a rotational speed set by the machining
speed set value 2. Further, the frequency component of the radial
direction displacement is obtained by performing Fourier
transformation on the time-series variations. For example, in a
case where the sectional shape after the process on the workpiece
12 to be machined is elliptical and the rotational speed command
value for the rotation-cutting main shaft 11 is S revolutions per
minute, the radius varies in a form like a sine wave over two
periods from 0 [seconds] to 60/S [seconds]. Accordingly, the
frequency component contained in the time-series variations of the
radial direction displacement is a component with a period of 30/S
[seconds], i.e., a frequency of S/30 [Hz].
FIG. 3 is a graph illustrating a frequency analysis result obtained
by the frequency analysis unit 4 in the first embodiment. In an
actual process, the deflection angle corresponds to the rotational
angle of the rotation-cutting main shaft 11; and the radial
direction displacement corresponds to the position of the
rectilinear shaft for driving the tool rest 14. Further, in the
first embodiment, the tool rest drive unit 13 is a control system
for performing position feedback control, and the feedback control
system is assumed to perform proportional control with a feedback
control gain K. In this case, the position response characteristics
of the control system of the tool rest drive unit 13 include the
characteristics of a low-pass filter with a cutoff frequency of K
[rad/s]. Here, when the cutoff frequency of K [rad/s] is converted
into units of Hz, it comes to K/2.pi. [Hz]. The movable shaft
parameter 3 includes the feedback control gain K for the tool rest
drive unit 13. In this case, the tool rest drive unit 13 cannot
catch up with a command of the control system that contains a
frequency component higher than the cutoff frequency of K.
The process diagnosis execution unit 5 diagnoses the propriety of
the process under a condition of the machining speed specified by
the machining speed set value 2, i.e., the rotational speed of the
rotation-cutting main shaft 11, by using the frequency component
calculated by the frequency analysis unit 4 and the feedback
control gain K included in the movable shaft parameter 3. In the
first embodiment, because the frequency component is S/30 [Hz], if
this is smaller than the cutoff frequency of K/2.pi. [Hz]
determined from the feedback control gain K of the tool rest drive
unit 13, the process can be performed. Accordingly, if the
rotational speed S of the rotation-cutting main shaft 11 is not
more than 15K/.pi. revolutions per minute, the process can be
performed. For example, in a case where the feedback control gain K
is 314 [rad/second], if the rotational speed of the
rotation-cutting main shaft 11 is not more than 1,500 revolutions
per minute, the process is diagnosed to be performable; and, if the
rotational speed of the rotation-cutting main shaft 11 is more than
1,500 revolutions per minute, the process is diagnosed to be
unperformable. Further, the process diagnosis execution unit 5
outputs a diagnosis result that the rotational speed of the
rotation-cutting main shaft 11 with which the process can be
performed is not more than 1,500 revolutions per minute. The output
diagnosis result is displayed by a display (not shown), for
example. The display can be a display included in the vibration
cutting process diagnostic device.
In the first embodiment, the mechanism by which the tool rest 14 is
reciprocated in the radial direction by the tool rest drive unit 13
can be realized by a shaft member present between the tool rest
drive unit 13 and the tool rest 14 such that the shaft member makes
a rectilinear reciprocating motion in the radial direction.
Alternatively, this mechanism can be realized by a shaft member
disposed on a side of the tool rest 14 opposite to the
rotation-cutting tool 15 such that the shaft member makes a
rectilinear reciprocating motion in the radial direction.
In the first embodiment, the vibration cutting process diagnostic
device 10 can be realized by a computer, for example. In this case,
the shape data 1 and the machining speed set value 2 are input via
a keyboard, which is an example of an input device, connected to
the computer and are stored in storage inside the computer. The
frequency analysis unit 4 and the process diagnosis execution unit
5 are realized by the CPU (Central Processing Unit) of the
computer. The diagnosis result output from the process diagnosis
execution unit 5 is output to a display monitor, which is an
example of an output device, connected to the computer and is
displayed thereby. The movable shaft parameter 3 is input from the
tool rest drive unit 13 and is stored in storage inside the
computer.
As described above, according to the first embodiment, the
propriety of the vibration cutting process under a specified speed
condition can be diagnosed in advance of the process being
performed. Further, because the upper limit value defining a range
of the machining speed that makes the process performable can be
understood in advance of the process being performed, the machining
speed can be determined without performing a trial process.
Further, according to the first embodiment, when a reference-model
following control or position proportional control, which is an
example of a control system having a low-pass filter
characteristic, is used, the propriety of the vibration cutting
process can be diagnosed.
Second Embodiment
The configuration according to the second embodiment differs from
the configuration according to the first embodiment in that the
control system of the rectilinear shaft of the tool rest, which is
a movable shaft, is a control system composed such that it uses a
feed-forward control and a notch filter. The position response
characteristics of the control system of the tool rest drive unit
13 are the characteristics of a band elimination filter that
attenuates the gain of a frequency band specified by a parameter of
the notch filter. The movable shaft parameter 3 includes the cutoff
frequency band of the band elimination filter. The cutoff frequency
band of the band elimination filter is assumed to be such that the
lower limit is F.sub.min [Hz] and the upper limit is F.sub.max
[Hz]. Further, the frequency component of a radial direction
displacement in the sectional shape of a workpiece 12 to be
machined is assumed to include a harmonic component twice as large
as the rotational frequency of the rotation-cutting main shaft
11.
FIG. 4 is a graph illustrating a frequency analysis result obtained
by the frequency analysis unit 4 in the second embodiment. In the
process diagnosis execution unit 5 according to the second
embodiment, if a frequency of S/30 [Hz] or S/15 [Hz] falls within a
range between F.sub.min [Hz] or more and F.sub.max [Hz] or less,
which is the cutoff frequency band of the band elimination filter,
then the process is diagnosed to be unperformable; and, if the
frequency does not fall within the range, the process is diagnosed
to be performable. Specifically, in the process diagnosis execution
unit 5, if the revolution number of the rotation-cutting main shaft
11 falls within a range between 15F.sub.min revolutions per minute
or more and 15F.sub.max revolutions per minute or less, or a range
between 30F.sub.min revolutions per minute or more and 30F.sub.max
revolutions per minute or less, then the process is diagnosed to be
unperformable; and, if the revolution number of the
rotation-cutting main shaft 11 does not fall within these ranges,
the process is diagnosed to be performable. For example, in the
case of F.sub.min=29 [Hz] and F.sub.max=31 [Hz], if the rotational
speed S of the rotation-cutting main shaft 11 is 450 revolutions
per minute or 900 revolutions per minute and further if the
rotational speed S falls within a range between 435 revolutions per
minute or more and 465 revolutions per minute or less or a range
between 870 revolutions per minute or more and 930 revolutions per
minute or less, then the process diagnosis execution unit 5 outputs
a diagnosis result that the process is unperformable. The output
diagnosis result is displayed by a display (not shown), for
example. The display can be a display included in the vibration
cutting process diagnostic device.
As described above, according to the second embodiment, the
propriety of the vibration cutting process under a specified speed
condition can be diagnosed in advance of the process being
performed. Further, because a range of the machining speed that
makes the process performable can be understood in advance of the
process being performed, the machining speed can be determined
without performing a trial process. Further, according to the
second embodiment, when a command notch filter, which is an example
of a control system having a band elimination filter characteristic
is used, the propriety of the vibration cutting process can be
diagnosed.
Third Embodiment
The configuration according to the third embodiment differs from
that of the first embodiment in that machine anti-resonance is
present in the shaft feeding system of the rectilinear shaft of the
tool rest, which is a movable shaft. The position response
characteristics of the rectilinear shaft include a characteristic
in which the gain is lowered at an anti-resonance frequency. In the
third embodiment, the sectional shape of a workpiece to be machined
is the same as that of the workpiece according to the first
embodiment; and the frequency component contained in a position
command signal is assumed to be that illustrated by FIG. 3.
The movable shaft parameter 3 includes the anti-resonance frequency
of a mechanical system; and this anti-resonance frequency is
denoted by F.sub.a [Hz]. In the process diagnosis execution unit 5
according to the third embodiment, if a frequency of S/30 [Hz] is
equal to F.sub.a [Hz], which is the anti-resonance frequency of the
rectilinear shaft of the tool rest 14, the process is diagnosed to
be unperformable; and, if the frequency is not equal to F.sub.a
[Hz], the process is diagnosed to be performable. Specifically, if
the revolution number of the rotation-cutting main shaft 11 is
30F.sub.a revolutions per minute, the process is diagnosed to be
unperformable; and, in the other cases, the process is diagnosed to
be performable. For example, in the case of F.sub.a=40 [Hz], if the
rotational speed S of the rotation-cutting main shaft 11 is 1,000
revolutions per minute, the process is diagnosed to be performable.
Further, in this case, the process diagnosis execution unit 5
outputs a diagnosis result that a value of the rotational speed S
that makes the process unperformable is 1,200 revolutions per
minute. The output diagnosis result is displayed by a display (not
shown), for example. The display can be a display included in the
vibration cutting process diagnostic device.
Note that, in the third embodiment, the anti-resonance frequency
included in the movable shaft parameter 3 has been described as a
single frequency F.sub.a, but the present invention is not limited
thereto. The anti-resonance frequency can be the upper limit
frequency or the lower limit frequency of a frequency band with
which the gain response of the mechanical system becomes not
greater than a set gain value.
FIG. 5 is a view illustrating an example of the gain response
characteristics of the mechanical system with respect to the
frequency. In a case where accelerance or inertance, which is the
gain response from the drive force to acceleration of the
mechanical system, has a characteristic as illustrated in FIG. 5,
if an anti-resonance range is defined by a frequency band with a
gain of -3 dB or less, then the upper limit frequency is 43 Hz and
the lower limit frequency is 37 Hz. In this case, if the rotational
speed S falls within a range between 1,110 revolutions per minute
or more and 1,290 revolutions per minute or less, a diagnosis
result is output indicating that the process is unperformable.
As described above, according to the third embodiment, the
propriety of the vibration cutting process under a specified speed
condition can be diagnosed in advance of the process being
performed. Further, because the range of the machining speed that
makes the process performable can be understood in advance of the
process being actually performed, the machining speed can be
determined without performing a trial process. Further, according
to the third embodiment, when the mechanical system has
anti-resonance characteristics, the propriety of the vibration
cutting process can still be diagnosed.
The configurations illustrated in the above embodiments are merely
examples of the contents of the present invention, and they may be
combined with other known techniques. Further, the configurations
can be partly omitted or changed without departing from the spirit
of the present invention.
REFERENCE SIGNS LIST
1 shape data, 2 machining speed set value, 3 movable shaft
parameter, 4 frequency analysis unit, 5 process diagnosis execution
unit, 10 vibration cutting process diagnostic device, 11
rotation-cutting main shaft, workpiece, 13 tool rest drive unit, 14
tool rest, 15 rotation-cutting tool.
* * * * *